X17 XCLUSIVE - Lindsay & Sam Fight Over Infidelity!

Confessions of a 22-year-old drama queen!

After her assistant banged up her Maserati yesterday, you'd think Lindsay Lohan's day couldn't get any worse, but naturally, it did. Last night, Lindsay and Samantha had one of their infamous screaming catfights, and around 10:30pm a locksmith showed up! Samantha told photogs outside that she locked herself in the bathroom, and though Linds wouldn't come out of the house, eyewitnesses could hear her crying and screaming, "I never cheated on you!"

X17 photogs tell X17online exclusively:

"It sounded like Lindsay was going crazy in there - like a toddler throwing a temper tantrum. We've heard them fight before, but they've never had to call someone to the house like this!"

Sam seemed calm and collected when she emerged from her house half an hour later, but we're being told that she may have locked herself in the bathroom to get away from Lindsay, and that it was LINDSAY who called the locksmith to open the door.

Sam left the house at 11pm for her DJ gig at One Sunset, and Lindsay stayed behind. Maybe Sam put her on time out?